Study Discovers Link Between Increased White Matter in the Brain
and Poor Motor Skills in Children With Autism

Research Conducted at the Kennedy Krieger Institute Examines How
Motor Skill Deficits Can Provide Insight Into the Brain Basis of
Autism

BALTIMORE, July 30, 2007 /PRNewswire-USNewswire/ -- A study
published in the August issue of the journal Brain demonstrates,
for the first time, an association between increased white matter
volume and functional impairment in children with autism. Findings
from researchers at the Kennedy Krieger Institute in Baltimore,
Md., reveal that in children with autism, increased white matter
volume in the motor region of the brain predicts poorer motor
skills. Conversely, in typically developing children, increased
white matter volume predicts improved motor skills, with a similar
association observed in children with attention
deficit/hyperactivity disorder (ADHD). The relationship between
increased white matter volume and functional impairment, which
appears to be specific to autism, may be representative of global
patterns of brain abnormality in autism that not only contribute to
motor dysfunction, but also to deficits in socialization and
communication that define the disorder.

Children with autism are typically motorically clumsy and
awkward, similar to how they are socially clumsy and awkward. They
often experience difficulties with basic motor control and with
learning more complex motor skills, such as riding a tricycle,
pumping their legs on a swing or buttoning, zipping and tying shoe
laces. Additionally, high-functioning children with autism often
excel in academic areas, such as math, as opposed to athletic
activities, such as baseball. Because measures of motor function
are highly quantifiable and reproducible, they are much easier to
study than measures of social and communication behavior. Motor
signs can serve as markers for deficits in parallel brain systems
important for control of socialization and communication.

Researchers utilized anatomic magnetic resonance imaging (aMRI)
measures to study 76 children ages 8-12 years, including: 20
high-functioning children with autism; a control group of 36
typically developing (TD) children; and a clinical control group of
20 children with ADHD, a developmental disorder which, like autism,
has been found to be associated with impairments in motor execution
and control. Findings show a robust association between increased
white matter volume and basic motor skill impairment in children
with autism, which suggests that it may be a defining biological
feature of the disorder. Results demonstrate that the association
of increasing white matter volume and poor motor function appears
to be specific to autism, as this association was not observed in
the TD or ADHD groups.

"Carefully examining systems responsible for controlling simple
aspects of behavior, such as basic motor control, can provide a
window into understanding the systems that are responsible for
control of more complex social and communicative behavior," said
Dr. Stewart H. Mostofsky, lead study author and a pediatric
neurologist in the Department of Developmental Cognitive Neurology
at the Kennedy Krieger Institute. "This finding is an important
step forward and will guide future research into the abnormalities
associated with socialization and communication that define the
disorder."

Motor impairments, such as those seen in autism, offer valuable
insight into the neurologic basis of developmental disorders. This
is especially critical for autism and other disorders where the
neurologic basis is not well understood. The most consistent
neuroimaging finding in children with autism is increased brain
volume, which has been primarily attributed to an increased volume
of white matter (white matter consists of the connections between
brain regions). To address the current lack of evidence showing
that increases in white matter volume are associated with
functional impairment in children with autism, researchers in this
study examined associations between motor skills and white matter
volume.

Researchers assessed participants' basic motor skills using a
standardized motor examination for children, the Physical and
Neurologic Examination of Subtle Signs (PANESS), which has been
used in past studies to demonstrate basic motor skill impairments
in children with autism and ADHD. With the PANESS, higher scores
indicate poorer performance. Consistent with previous findings,
children with autism had significantly poorer motor performance
(higher PANESS scores) than TD controls. Researchers identified a
strong positive correlation between total PANESS score and white
matter volume, revealing that increased white matter volume
predicted poorer motor skills in these children.

In contrast to the children with autism, TD children showed a
significant correlation in the opposite direction, with increased
white matter volume predicting better motor skills (lower PANESS
scores). The correlation in children with ADHD was considerably
different from the children with autism and similar to the TD
group.

In the future, Dr. Mostofsky and his colleagues hope to examine
correlations of brain structure with motor performance using
imaging techniques, such as diffusion tensor imaging (DTI), which
can provide additional information about white matter connections.
Upcoming studies may also extend this research to younger children
and investigate, from a developmental perspective, what contributes
to impaired acquisition and learning of motor skills in children
with autism. Additionally, the brain systems involved in motor
skill learning appear to be important for learning aspects of
socialization and communication, including language. Future
research that examines how these learning systems are affected in
children with autism could therefore provide crucial information
about the brain basis of the disorder and prove very valuable in
guiding, and ultimately improving, therapy.

About Autism

Autism spectrum disorders (ASD) is the nation's fastest growing
developmental disorder, with current incidence rates estimated at 1
in 150 children. This year more children will be diagnosed with
autism than AIDS, diabetes and cancer combined, yet profound gaps
remain in our understanding of both the causes and cures of the
disorder. Continued research and education about developmental
disruptions in individuals with ASD is crucial, as early detection
and intervention can lead to improved outcomes in individuals with
ASD.

About the Kennedy Krieger Institute

Internationally recognized for improving the lives of children
and adolescents with disorders and injuries of the brain and spinal
cord, the Kennedy Krieger Institute in Baltimore, Md., serves more
than 13,000 individuals each year through inpatient and outpatient
clinics, home and community services and school-based programs.
Kennedy Krieger provides a wide range of services for children with
developmental concerns mild to severe, and is home to a team of
investigators who are contributing to the understanding of how
disorders develop while pioneering new interventions and earlier
diagnosis. For more information on Kennedy Krieger Institute, visit
http://www.kennedykrieger.org.